With various vehicles operated on and off the highway, there is a problem in meeting weight restrictions for highway use. These problems have been overcome by use of what is termed a load booster wheel assembly which is simply an auxiliary set of wheels which can be loaded when the vehicle is operated on the highway so as to take up part of the load and bring the loading on each axle into legal restrictions. When the vehicle is to be operated off the highway, generally these load booster wheels are desirably taken out of operating position to minimize the risk of damage to the wheel assemblies and to increase the mobility of the vehicle.
The prior art approach is that the load booster wheels have frequently been carried by a wheel support assembly actuated to its operating position by an air bag positioned near each end of the axle. These arrangements have a failing in that when the wheel assembly is hoisted vertically to its inoperative position there is not enough clearance between the hoisted wheels and the ground or ground structure to achieve maximum mobility for positioning the truck and to prevent or minimize risk of damage to the booster assembly. It is true that the booster assembly is generally carried on an auxiliary frame which can be moved to a desired rearward position for use and brought forwardly to take the wheels closer to the fixed rear axles, but this still does not overcome the problem of lack of mobility and damage to the booster assembly. Up to now there has not been adequate vertical travel of the load booster wheels between the operating and the inoperative positions.
Attention is directed to examples of prior load booster wheel assemblies such as those just described, and which are disclosed in the following U.S. patents:
______________________________________ Granning 3,133,745 Issued May 19, 1964 Granning 3,325,181 Issued June 13, 1967 Granning 3,689,102 Issued September 5, 1972 Granning 3,713,663 Issued January 30, 1973 Granning 3,747,948 Issued July 24, 1973 ______________________________________